Surprised so many people seem to like this, just got done with it and it's genuinely awful. Puzzles of any realistic kind, gone, big cavernous tombs/hidden treasures, gone. Difficult to climb large scale areas, gone. Interesting characters gone, they are all skin deep and randomly get angry at each other for completely standard actions.
Someone robs a bank, kills Templar, that is what assassins do, but somehow it was bad. Ridiculous working with rival gang out of nowhere, shockingly goes bad. Completely un-epic ending, incredibly boring and slow final mission, with no difficulty or complexity followed by a final fight that had no actual difficulty, was 90% scripted and constantly interrupted to make it feel insanely dull.
Then we get into difficulty, there wasn't any, even compared to the other ones. You get loads of things that let you kill everyone, massive healing(though you'll almost never need it), you can hire people everywhere to basically do everything for you if you really wanted.
The modern day bits, the abysmally cheap sometimes the 'modern day' parts are a screen with the assassins creed logo on it with a voice over the top. The most tedious and boring version yet. Absurdly easy to get money, absurdly easy to get and buy every single upgrade. Some of the extra stories, some of the Darwin stuff wasn't only boring, it was rubbish and poorly written.
Unity may have run like crap but it wasn't nearly as dumbed down overall.
It's this constant irritating trend, the map must be bigger, there must be more to collect, but less tombs, less puzzles, less good stories. It's all about size over quality in almost everything now.
Black Flag was great, story was 100 times better, characters were 100 times better, the building an empire was better, combat was better on foot, the sailing was great. Upgrades felt harder to find, most of the important ones being under the ocean rather than "hold E to unlock".